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People have been talking about strange underwater sounds for thousands of years, but it took until the mid-20th century for scientists to identify one of the causes: whale calls, whistles, and blue calls. I did.
How some whales make this sound remains a mystery. A study published in the journal Nature on Wednesday offers a new explanation: The three dead whales were discovered thanks to a device that forced air through their vocal boxes.
The voice box, or larynx, is an ancient organ. “It evolved when fish crawled out of the ocean and animals needed a way to separate the air they breathed from the food they consumed,” said Koen Elemans, study author and professor of biology at the university. Stated. in southern Denmark.
The larynx acts like the anterior chamber of the trachea, or trachea, and a flap of tissue called the epiglottis prevents food and drink from falling into the trachea. Mammals have evolved additional folds of tissue called vocal folds, or vocal cords, just below the epiglottis, where air exhaled from the lungs vibrates to produce sound.
When the land-dwelling ancestors of whales returned to life in the sea, “they basically had to replace their larynx, because when these animals were breathing on the surface, they lost their larynx very quickly. That’s because you have to expel a lot of air,” Dr. Ellemans said. Vocal cords like those of land mammals can get in the way.
Like sperm whales and dolphins, toothed whales use their larynx like a cork to seal off their airways. They evolved a way to produce sound in their nasal cavities instead. But scientists suspected that filter-feeding baleen whales, such as musical humpback whales and giant blue whales, still use vocal organs.
These whales are too large to be kept in captivity and tend to make most of their vocalizations underwater, where it is too deep for divers to collect ultrasound or MRI data. Instead, Dr. Elemans and his colleagues considered the next best option. They were freshly preserved audio boxes dissected from three baleen whales (two in Denmark and one in Scotland) that died after stranding on beaches. One was a humpback whale, another was a mink, and the last one was a sei.
The researchers attached a two-foot-long whale vocal box to a series of pipes and pumped air through it. At first, there was no sound coming from the voice box. But when the researchers repositioned the larynx so that the fat pads attached to it vibrated against the vocal cords, the lab was filled with whale sounds.
In terms of excitement among researchers in the lab, “on a scale of 1 to 10, it was an 11,” said study author W. Tecumseh Fitch, a professor of cognitive biology at the University of Vienna. . This means of producing sound by forcing air between a cushion of fat and the vocal cords has never been seen in any other animal.
Joy S. Reidenberg, a professor of anatomy at the Icahn School of Medicine at Mount Sinai who was not involved in the study, said the experiment “changes our view of how these whales make sounds. “and perhaps show the mechanism.” Whales may use it to make multiple sounds at the same time. ”
He said the study was limited by the small number of whale vocal boxes available for analysis, and it would be beneficial to examine more specimens, especially adult male humpback whales that produce complex songs. He pointed out that there is a possibility.
The researchers also created a digital model to examine how lung capacity and water pressure constraints affect where and how whales sing. The results of this study suggest that whales sing only in shallow waters. Unfortunately, this is also a place where noise from human activities, such as shipping, can interfere with whale calls.
Christopher W. Clark, a professor emeritus of neurobiology and behavior at Cornell University who was not involved in the project, said the complexity of sound traveling through water means that whales’ ability to communicate is more likely to be disrupted by ship noise the younger they are. He said there is a possibility that there will be no. Research suggests.
And the study provides a “road sign” for researchers to focus on to learn how and where whales actually communicate with each other, he said. said.
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